BOSTON — It’s the worst-kept secret of the 2012 campaign: The candidate who does the least public media-bashing — Mitt Romney — has the worst relationship of all with the press.

But as Romney seeks to nail down the GOP nomination and cement the narrative that the delegate math makes it nearly impossible for his remaining rivals to surpass him, his campaign has launched what passes for a media charm offensive.

Senior staff is suddenly more accessible. The Commercial Street headquarters in Boston is no longer off-limits. This week featured a happy hour with the traveling press at a downtown Boston pub and Romney himself broke with campaign precedent by visiting the back of the campaign’s charter airplane for a rare chat with reporters Tuesday before a flight from Ohio to Massachusetts.

After months of near-toxic relations between the famously controlling and tightly-scripted campaign and its traveling press corps, it represents a détente of sorts.

The “evolution,” as one adviser described it, marks a significant shift away from a previous posture marked by relative inaccessibility to top campaign officials and periodic emails from the campaign’s high command questioning the professionalism of reporters who authored stories or tweets with which the campaign disagreed.

Prior to the new, informal initiative the campaign’s press aides routinely ignored e-mails and phone calls from reporters, even on the most routine matters. Information about schedules and cities in which events would take place were closely held and often released with less than 24 hours notice.

That approach put them at variance with Newt Gingrich and Rick Santorum, who have made their brand of media-bashing performance art a centerpiece of their campaigns. While the former Massachusetts governor has never made press criticism a staple of his stump speech, Gingrich and Santorum have regularly been far more accessible to the national traveling press than Romney. Relations between their campaigns and the media have also been notably looser and less confrontational.

Romney’s poorly-received Feb. 24 economic speech at Ford Field in Detroit represented a low point in the press-campaign relationship, and served as a catalyst for the new direction. That day, reporters who asked the campaign for clarification on what new proposals would be embedded within the speech found no one at the campaign who would explain them.

The vast majority of reports that day — including those on the evening TV network news casts — ended up focusing on the theatrics of the event: Romney speaking to 65,000 empty seats in the cavernous football stadium.

That night, a senior campaign official addressed a gaggle of reporters in the spartan lobby of the Lansing Courtyard by Marriott, apologizing to reporters for failing to provide access to the campaign’s chief policy advisers or press aides who could provide context for the event or explain what, exactly, was supposed to be new in the seemingly routine Ford Field speech.

The official pledged to arrange more conference calls with senior campaign officials to explain strategy and new policy statements. At the same time, two Romney advisers who are veterans of several presidential campaigns past were pushing the press shop to seek a thaw in relations with reporters.

Romney himself realized, in the days after the Ford Field p.r. debacle, that his relations with the press were in serious need of repair, one adviser said, and agreed to participate in the effort to rebuild the campaign’s relationships with reporters.

“We can’t be at war with each other,” one of the veteran advisers said. “Every moment of every day doesn’t have to be competitive or tinged with us-against-them.”

The first expressions of the campaign’s new approach surfaced in advance of Super Tuesday. Romney senior strategist Russ Schriefer and senior aide Eric Fehrnstrom were dispatched on troubleshooting missions last weekend. Schriefer dined with print reporters Thursday night in Bellevue, Wash., and Fehrnstrom hosted a dinner for the television embeds Monday in Columbus, Ohio.

Both senior staffers sat into the wee hours with more than a dozen members of the traveling press in the bar of the Cleveland airport Sheraton Friday night. And Fehrnstrom appeared at an off-the-record Saturday night dinner in Cincinnati hosted for national reporters by Ohio Sen. Rob Portman.

At those encounters with Schriefer and Fehrnstrom, reporters ticked off some of their complaints, among them the fact that the campaign frequently scheduled conference calls at times when the traveling press would be in flight or during Romney events, when the traveling press would not be able to participate.

Fehrnstrom, who regularly reminds reporters of his long-ago tenure at the Boston Herald, agreed to have the calls arranged at times convenient for the campaign’s press corps.

“I wanted to meet with people in groups and individually just to find out how things are going,” Fehrnstrom told POLITICO Wednesday. “Yeah, we’re constantly refining and making improvements because we want a positive relationship with the press. We know that doesn’t mean every article is going to be glowing. There will be tough articles, but that’s your job, we want to help you do the best job that you can do.”

There was also, after a series of requests from reporters, a Saturday afternoon conference call with the campaign’s national counsel Ben Ginsberg to explain the delegate situation in Ohio, where Santorum was ineligible to win delegates in certain congressional districts.

The campaign pointed out that the call had been scheduled during a two-hour down period during which the traveling reporters could listen.

Romney himself remains relatively off-limits for on-the-record questioning. His interviews in recent weeks have almost all gone to friendly cable television hosts and local media reporters. His press conferences after voting Tuesday in Belmont, Mass., with the traveling press was just the second since Feb. 8, when he spoke with reporters on the Atlanta airport tarmac after losing three states to Santorum the day before.

But when campaign officials were miffed that Super Tuesday coverage focused more on Romney’s failure to win a decisive victory in Ohio than his victories in six states and significant delegate margin, the torrent of angry e-mails that marked the Michigan campaign did not materialize in reporters’ in-boxes.

And on Wednesday, the campaign invited reporters inside its Boston headquarters here for a 30-minute briefing on the delegate count and Romney’s path to the nomination. The campaign also hosted a Wednesday evening happy hour with the traveling press at a Scholars, a Boston pub where officials ranging from the deputy campaign manager, Katie Packer Gage, to senior advisers, strategists and longtime Romney friends and aides on down to the regional and traveling press secretaries with whom reporters spar on an hourly basis, schmoozed over pints.

“The bottom line is we want a good relationship with the press,” Fehrnstrom said. “We know there’s always room for improvement. And while the relationship is meant to be adversarial, we want to be as helpful as we can. We think the more information and the better information you have, the more informed your reporting will be.”